Look to the sky for the Hunter's Moon

Republican Photo by Patrick RowanA rising Hunter's Moon glows over bare trees in a local cemetery.

By Patrick Rowan

It seems almost silly to ignore here the recent evidence that sub-atomic particles called neutrinos appear to be breaking the light speed barrier by a tiny yet significant amount, but there’s probably not much point until the claim is either confirmed or discredited (as many scientists suspect it will be). If confirmed, it could be the most radical shakeup in physics since Einstein published his general theory of relativity 95 years ago.

So, on to the current topic.

Do you remember when you first noticed the moon? How about when you realized that it wasn’t always there at night? Or that it changed shape? Or that it could sometimes be seen in the daytime? Do you now take it for granted?

The organizers of “International Observe the Moon Night” hope to shake people out of that last state. On Saturday, folks around the world are encouraged to get out and take a new look at our nearest neighbor in space – to appreciate it, and learn more about it.

Widely considered as not much more than a dead rock orbiting Earth, the moon was largely neglected for decades by our unmanned space program. And now, almost 40 years after the last humans set foot there, there is renewed interest in that world on our doorstep.

If skies are not too cloudy this evening at dusk, look for the 69-percent illuminated moon in the southeast. Between 8 and 9 p.m. it will have climbed about a third of the way up in the south – its highest for the night. After that, it slides westward and lower, disappearing in the southwest an hour or so after midnight. (During this same period, you can’t miss bright Jupiter ascending in the east.)

The moon may be on its way down in late evening, but don’t worry, it’s a waxing moon – meaning it will be back the next night even more full. Add to that the fact that it will also be crossing our skies higher and staying up later each night for the coming week or so, and you’ve got the “fall moon effect.” At this time of year, near-full moons seem not to want to give up their hold on our evening skies. They don’t rise as much later each night as at other times of year.

NASA PhotoTechnicians add a payload fairing to the GRAIL booster.

Probably the Harvest Moon is best known for this. But this year’s Harvest Moon – the full moon closest to the fall equinox – was last month. So, early as it is (on Monday), this month’s full moon is the Hunter’s Moon. The effect of both moons is similar.

Plan now to get out and enjoy these earlier nights with their increased lunar presence. It’s a unique time of year, with dark coming before bedtime, but often with tolerable temperatures – and usually no bugs. Usually.

It’s a winding down from summer, and a gearing up for winter. Perhaps this has something to do with why soaking in as much moonlight – and for as many nights in a row as possible – has become something of an autumn compulsion for this skywatcher. It’s a time when I find being indoors, when beautiful moonlight is shining outside, difficult. As the sun lightens it grip, I embrace the moon.

But just seeing the moon’s bare sunlit surface isn’t good enough; I have to be where there are no electric lights ruining the subtle delicacy of a moonlit landscape. I want to see mymoon shadow; to walk by moonlight alone.

It’s hard to imagine, but the moon wasn’t always there. On the other hand, some are looking at the possibility that there may have actually been two moons. That would have been, of course, once upon a time – a very long, long time ago.

In either case, we are more immediately connected physically with the moon than the sun. The soles of your shoes have some of the same stuff on them as the 12 astronauts who moon-walked four decades ago did there. The moon and Earth were once one and the same.

The composition of samples that Apollo astronauts carried home helped establish that the moon and Earth have a common ancestry. The moon, it would seem, may well have been blasted off the Earth when a Mars-sized asteroid collided with our planet some 4.5 billion years ago. That would have mixed things up a bit.

Our little neighborhood was a chaotic mess of vaporized Earth and impactor material blending together. Some was ejected into space, speeding off never to return, and most of the heavy stuff fell back to Earth over time. Much of the rest, however – mostly from the impactor itself – had just the right speed and trajectory to stay in orbit.

Over millions of years, the orbiting debris coalesced to form our moon. In this scenario, the Earth and moon would contain a mish-mash of each others’ materials, which is what the Apollo lunar samples showed. So we’re sort of the same, although not quite. Interestingly – with a mass-to-mass ratio unique to the solar system – some consider the Earth and its moon almost a double planet. (Pluto and its moon Charon are even closer in size and mass, but are not considered “rocky” planets.)

After the collision, both Earth and its new moon would have had molten surfaces, and would bear little resemblance to what is here today. Both were hellish and lifeless.

Now, billions of years hence, only the moon remains lifeless – we think. And we on Earth have grown accustomed to seeing just one of its faces. It’s really quite odd when you think about it.

Until the Soviet Union’s Luna 3 probe swung past the moon in 1959 (52 years ago, almost to the day) and snapped a couple of low-quality images of “the farside,” we had no idea what the place looked like. (The pictures were taken on ISO 35 photographic film, which was developed in an automatic onboard lab, then automatically scanned and televised back home.)

The first humans to lay eyes on the lunar far side were the crew of Apollo 8 in 1968, as they orbited – but did not land. It is strikingly different from the Earth-facing side. Mostly cratered and mountainous, there are no vast, smooth plains, the so-called lunar seas, or “maria.” These are the dark regions that give the “man in the moon” appearance.

So why this difference between the “front” and “back”? And how much does it have to do with the moon being tidally locked (showing only one side) with Earth? Just exactly how is mass distributed around the lunar globe? We already know it’s pretty lumpy.

The unmanned GRAIL (Gravity Recovery and Internal Laboratory) mission, which launched on Sept. 10 and is currently following a convoluted, fuel-saving, months-long route to the moon – should help answer these and other questions. GRAIL consists of two probes, A and B, which will orbit the moon in tandem beginning Dec. 31 and Jan. 1, respectively. Ultra-precise measurements of the distance between them – and hence their speed relative to one another – will reveal variations in the moon’s gravitational pull, which in turn will allow researchers to map the moon’s interior structure.

We’ll soon have a good idea of how deep the mantle is, where the highest concentrations of mass are, and how big the moon’s core is.

On Saturday night, “International Observe the Moon Night,” the moon will be 91 percent full. It will climb until it is about halfway up in the south in later evening, closely followed by beaming Jupiter. Can you see the bright star Fomalhaut well below the moon? After cresting at around 10:30 p.m., the moon will slide to the western horizon before sunrise.

If you miss it that night, try the next. Notice how the moon gets closer to Jupiter each evening. Jupiter, by the way, will be at opposition later this month, and about as bright and close as it has been any time in the past decade. These are great nights to dust off that telescope and give this giant planet and its moons a look.

Weather permitting, the Springfield Stars Club will observe the moon during their Stars Over Springfield public observing program this Friday evening at the Springfield Science Museum.

The Stars Club will also hold an International Observe the Moon Night at their Stars Over Agawam program on Saturday from 7 to 9 p.m. at the School Street Park (back field). A $5 per family donation is requested.

Also on Saturday, the Amherst Area Amateur Astronomer’s Association will hold their weekly public observing at 9 p.m. at the Wilder Observatory off Snell Street in Amherst. Members set up their own scopes on the lawn outside the observatory for public use as well. This program is free, and for all ages.

Find rise and set times for the sun and moon, and follow ever-changing celestial highlights, in the Skywatch section of the Weather Almanac in the daily Republican and Sunday Republican.

Patrick Rowan has written Skywatch for The Republican since 1987 and has been a Weather Almanac contributor since the mid 1990s. A native of Long Island, Rowan graduated from Northampton High School, studied astronomy at the University of Massachusetts-Amherst in the ¤’70s and was a research assistant for the Five College Radio Astronomy Observatory. From 1981 to 1994, Rowan worked at the Springfield Science Museum’s Seymour Planetarium, most of that time as planetarium manager. Rowan lives in the Florence section of Northampton with his wife, Clara, and cat, Luna.